Annotated configuration files: add note about preferred chunk server authentication method.
Chunk server: fix theoretically possible assertion failure in replication code path when read completion is invoked with replication already canceled, and the read op was issued with no disk checksum verification flag set, and the checksum verification has failed.
Tools: deprecate qfsping. Emit error message if ping is invoked with chunk server and authentication enabled.
Meta server; add chunk server executable md5sum reported in chunk server hello to the chunk server ping and get chunk servers counters RPC responses.
Meta server: fix get chunk server counters response by adding missing column separator.
Merge branch 'master' into topic/cs_threads